Alzheimer?s disease (AD) is the most common neurodegenerative disease resulting in dementia, dependence and healthcare expenditure. Inflammation in the brain (neuroinflammation) shapes the course of neurodegeneration by impacting neuronal survival through pro-inflammatory (detrimental) as well as anti- inflammatory (protective) effects. Central nervous system (CNS) mononuclear phagocytes (CNS MPs) are comprised of CNS-resident microglia and CNS-infiltrating monocytes), and are primary enactors of neuroinflammation. Selective inhibition of pro-inflammatory CNS MPs in AD may slow down the rate of neurodegeneration and we have found that blockade of potassium channel Kv1.3 is a promising immune strategy in AD. Kv1.3 channels regulate calcium flux, are expressed selectively by pro-inflammatory CNS MPs in AD and their blockade in AD mouse models limits neuropathology. We hypothesize that Kv1.3 channels are key regulators of immune signaling and survival in pro-inflammatory CNS MPs in AD that can be therapeutically targeted by selective Kv1.3 blockers. In this proposal, we will tackle three specific questions related to the role of Kv1.3 channels expressed by pro-inflammatory CNS MPs in AD, with the overall goal of laying the pre-clinical foundation for future translation of Kv1.3 blockers to humans. First, we will perform in-vivo experiments using Kv1.3 blockers in the 5xFAD model of A? accumulation to identify immune signaling pathways in CNS MPs that require Kv1.3 channels (Aim 1a). We will also determine whether blockade of Kv1.3 decreases pro-inflammatory CNS MPs in the brain by increasing apoptosis and switching them towards anti-inflammatory profiles (Aim 1b). Next, we will test the hypothesis that CNS MPs expressing high numbers of Kv1.3 channels originate from blood monocytes, rather than microglia (Aim 2). We will perform transcriptomics of CNS MPs and blood monocytes and apply the irradiation bone marrow chimera model to determine whether CNS MPs in AD models originate from microglia or from blood monocytes that infiltrate the brain. In Aim 3, we will perform long-term in-vivo studies to test the efficacy of Kv1.3 blockers on behavioral and pathological endpoints in two AD mouse models and will perform mass spectrometry of cerebrospinal fluid to identify protein biomarkers associated with therapeutic effects of Kv1.3 blockers. Lastly, we will determine the role of CNS MP Kv1.3 channels in AD pathology using a conditional deletion genetic approach in AD models. To achieve the aims of this R01 proposal, we have assembled a multi-disciplinary team of investigators with expertise in neuro-immunology, Kv1.3 biology and mouse models of neurodegeneration (Dr. Rangaraju, PI), immune signaling (Dr Wood), mass spectrometry and biomarker discovery (Drs Seyfried and Levey) as well as small-molecule pharmacology (Drs. Wulff).